enginefacade is not compatible with python 3.7

[Eric Harney]

_TransactionContextManager has a @property/method named "async", which is a reserved keyword in python 3.7.

This results in:

--- import errors ---
Failed to import test module: oslo_db.tests.sqlalchemy
Traceback (most recent call last):
  File "/home/eharney/src/oslo.db/.tox/py37/lib/python3.7/site-packages/unittest2/loader.py", line 490, in _find_test_path
    package = self._get_module_from_name(name)
  File "/home/eharney/src/oslo.db/.tox/py37/lib/python3.7/site-packages/unittest2/loader.py", line 395, in _get_module_from_name
    __import__(name)
  File "/home/eharney/src/oslo.db/oslo_db/tests/sqlalchemy/__init__.py", line 16, in <module>
    from oslo_db.sqlalchemy import test_fixtures
  File "/home/eharney/src/oslo.db/oslo_db/sqlalchemy/test_fixtures.py", line 22, in <module>
    from oslo_db.sqlalchemy import enginefacade
  File "/home/eharney/src/oslo.db/oslo_db/sqlalchemy/enginefacade.py", line 968
    def async(self):
            ^
SyntaxError: invalid syntax

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/577323

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/577525

[OpenStack Infra (hudson-openstack)]

Change abandoned by Hervé Beraud (<email address hidden>) on branch: master
Review: https://review.openstack.org/577525
Reason: duplicate with https://review.openstack.org/#/c/577323/2

[OpenStack Infra (hudson-openstack)]

Change abandoned by Hervé Beraud (<email address hidden>) on branch: master
Review: https://review.openstack.org/577323
Reason: duplicate patch I close this patch
cf. https://review.openstack.org/574833

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/574833
Committed: https://git.openstack.org/cgit/openstack/oslo.db/commit/?id=df6bf3401266f42271627c1e408f87c71a06cef7
Submitter: Zuul
Branch: master

commit df6bf3401266f42271627c1e408f87c71a06cef7
Author: Mike Bayer <email address hidden>
Date: Tue Jun 12 13:26:39 2018 -0400

    Rename enginefacade.async to enginefacade.async_

    Python 3.7 now makes "async" a keyword, so deprecate the
    "async" name and replace with "async_". Additionally,
    use attribute name access only in order to implement and
    test "async" as it won't work under Python 3.7.

    Closes-Bug: #1775866
    Change-Id: Ifb2c59c2cfbd615b04570b31fcfe868f4ffea3c6

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/oslo.db 4.40.0 release.